Transformer-terminal.



' C. LE G. FORTESCUE.

TRANSFORMER TERMINAL.

nrmonxox PILBD me. 7'. 1911.

'Patented Feb. 23, 1915.

WITNESSS-z INVENTOR W ozw ATORNEY A UNI1ED STAIES PATENT OFFICE.

CHARLES LE G. FORTESCUE, OIE PITTSBURGH, PENNSYLVNA, ASSIGNOR T0 WEST-- INGHOUSE. ELECTRC AND MANUACTURING COMPANY, A. CORPORATION OF- TRANSFO Application filed August 7, 1911. Serial 0. 642,877.

T0 au whm it 17; ay concern Be it known that I, CHARLES LE G. Fon- TESCUE, a subject of the King of Great Britain, and a resident of Pittsburgh. in the county of Allegheny and State of PnnsyL high voltage service. and, at the same time.

'substantially preclude the concentration .of *electric stresses upon certain port1ons there0f.

Another object of my invention is to pro' vide a terminal structure of the character above-indicuted which also embodie a specially cobled conductin lead.

Insulating bushings or the terminal connections of a high voltage transformer, circuit breaker and other similar electrical ap paratus, are usually supported in the cover 01 top of the tank or casing in which the apparatus is located. "An electric device 10 cated in a tank or casing is usually immersed in an ins'ulating fluid, such as cil, which, at

the same time, may be utilized for.cooling.

purposes. It Wll be appurent,however, that my invention may be applied to electrical devices other than those immexsed in an in sulating fluid. Heretofore, insulating bushings were designed so as to have a suflicient t-hiCkness of di-electric material to resist the stresses imposed thereupon by the radial electrostatic limes emanating from the h igh potentxal conductors projecting through the of-electrostatic fines upon the insulator surfaces which resulted in the insulabor being subjected to concentrzited and'consequent alinormal electrostatic stresses;

I have discorered that, ifthe electrostatic flow lines inthe field external. tothe bushing are precluded;from concentrating upon surfaces of the bushing, the bshin g is capable of insulating conductors of potcntials higher than heretofore ntilized. I beliere thatthe' eflimency in-des1gn of a terminal must be considered both from the point of vi'ew of the efiectiveness of application of the insu- ]ating material around the lead, and also of the uniformity of stress in the region external to the terminal. c ordingly, the maximum insuluting strengtlt0f the busning ma -be obtained'if the external clectrostatic field is so distributed as t6createa uniform surface st1;esS upon the bushing. To attain this result 'tll the usual bushing, the space external tothe bushing must 'be bounded b two infinite parallel conducting planes verpendicular to the axis of the bushing. Inasmuch as such a structure is impraticable, I prode means whereby the electrostatic field is suificiently distribtd in order to secure a substantially unifor m surface distribution of the eleetrostatic stresupon the bushing. Although an entirely uniform surface stress is not obtained by means of niy'invention, it will be understo0d that undue concentra tions of electrostatic limes are precluded from forming upon the surfaces et insulating bushings, thereby admitting such bushings to be usedin insulating extremelg high voltage conductors.

Figure 1 of the accompanying drawings is a sectional elevation of a terminal structure embodying my invention. Fig. 2 is :1 sec tional view of a part of a modified form of the structure'of Fig. 1, and Fig. 3 is a plan view of the terminal.

\Vhile I have shown a bushing of the cond'enser type of construction, it is not in.- tended that myimention be limited to.terminals or outlet structures embodying condenser bushings only. Poreelain bushiugs, the well known oil filled type bushings, etc., may be efl'ectively used in my terminal structure. However, I have found that the condenser type bushing is particularly adapted for use in my structure becaus ze f its high insulating property, its light Welgllt,

Patented Feb.23, 1o15'.

and simplicity in construction. ccording to my present invention, I make the conducting lead of tubing and provide a hollow disk shape orsubstantially ellipsoidal body at its upper end which communicates with the tube. The lower end of the tube may be either open or closed as hereinafter pointed out, and the discoidal body is preferably sealed except for its opening into the tube.

Referring to Fig. 1, a terminal bushing 1 ing 1 and 15 sealed into a hollow ellipsoidal.

body 8 at its upper end. The central conducting lead 7 is provided with a. discoidal body 8 of conducting material at its outer end for the purpose of distbuting the elec-' trostatic field and preventing concentration of stresses at any point on the surface of the terminal bushing 1. The lower end of the tube Xtends into the oil 6 and is open so that if the air is once exhausted or excluded from the tube and the terminal 8, the oil Will be maint-ained therein. As before mentioned, it would be most desirable t0 bound the space external to the bushing l with two infinite parallel conducting planes perpendicular to the axis of the bushing. However, this is impracticable, butthe re sult obtained by that disposition of conduct 'ing planes may be sufliciently approximated for commercial conditions by dispoSing the conducting disk 8 and the substantiilly fiat conducting cover 4 of the case 5, as shown in the drawing. It is desirable that the cover 4 be so constructed as to have a minimum number of projecting surfaces or sliarp edges. The surfaces of the member 8 are so shaped as to relieve the electrostatic stresses that would otherwise exist in the air at the top end of the terminal, and also to redirect the eleetrostatic field that would otherwise exist adjacent to the surface of the bushing, so that the stresses imposed upon the bushing are substantially evenly distributed. To this end, the member 8 is extended laterally from the conductor 7 a distance that is large relative to the diameter of the conductor, and its edges are curved to present convex surfaces to the static field existing between it and the cover 4. The member 8 also has thin walls and a large major diameter relative to its thickness or depth, thereby providing a large radiating surface. Consequently, if the oil in the lower end of the tube becomes heated, it will rise and re place the much cooler oil contained in the closed member S. By this means, a circula- A tube 7 of contion is automatically maintained, the heat being conducted rapidl away through the gelatively thin walls of the hollow mem In Fig. 2, the tube 7, instead of being open at 1ts loWer end, is sealed by a plug 9, and the tube is filled with a fiuid 10 which may be either insulating or 'conducting, its sole purpose bein to transfer the heat from the conducting tube to the walls of the member 8 from Which it ma be readily radiated.

- the bushing intermediate its ends, of a laterally extendin flattened body upon the conductor that 15 convexly curved adjacent to its edges with respect to the said member.

2. The combination with a conductor, an insulating bushing surrounding the conductor, and a conducting member surrounding .the bushing intermediate its ends, of a substantially disk shaped body extending laterally from the conductor and having its edges curved convexly with respect to the said member.

3. The cmbination with a conductor, an insulating bushing surrounding the conductor, and a conducting member surrounding the bushing-intermediate its ends, of a conducting body extending latrally from the conductor and substantially parallel to the opposing surface of the said conducting member, the edges of the conducting body being curved convexly with respect to the said member.

4. The combination with a conductor, an insulating bushing surrounding the conductor, and a conducting member surrounding the bushing intermediate its ends, of a substantially disk shaped body extending laterally from one end of the conductor, said body having rounded edges.

5. The combination with a conducting tube, an insulating bushing theref0r composed 0f alternate layers of insulating :nd conducting materials, a conducting member embracing the bushing, of a closed hollow les conducting body extending laterally from posed of alternate layers of nsulating and condncting materlals, and a conducting memucr embracing the bushing, of a closed 4 the tube and hollow member are,filled.

7; T1c combination with :tconductor, and an insulating bushing surrounding the conductor comprising alternate layers of insulating and conducting materials, of a substantially discoidal shapcd conducting body extending laterally from the conductor, said body being convexly curved adjacent to its edgcs with respect tothe exposed surfaces of the bushing.

8. The combinatioh With a condnctor, and an insulating bushirig surrounding the conductor comprising alternate layers of insnlating and conducting matria ls, of a substantially discoidal shaped conducting body on one end of the bushing, said conducting bod v havirig it s cdges convexly curvcd with respect to the exposedsnrfiiccs ofthe bushing. V

9. The combination with a condnctor, and an insnlating bnshinp: surrounding, thc conducto'r comprising altcrnate layers of insnlating and 'condncting matvrials and having mm of its end portions stcmwd and in snbstantially thc fq.rm of a trnnqated conc, nf a snstantially discoidal shapcd conduct- Eng: b0dy oxtcnding ]atcrally fmm thc condm;tmg said Imdy hoing cbnvcxly cnrvcd adjacent to its cdgcs with respect to th 0):- pos0d snrfaccs of the lmshing.

10. The combinatiun with a cnnductm, and an insniating Innshim: sim*mmding thc conductor cmnprising alterna: ]ayors 0f insulating and conducting matvrials and having ont! of its ond parlions shapod in sm stantially thc i'nrm 01 a tr'nncatod cone,

of a substantially discoidal shaped conductingbody extending laterally from the conductor and disposed adjacent to one end of said bushing, the conducting body being convexly curvcd adjacent to its edges with respect to the exposed surfaces of the bushing.

11. The combination with a conductor, an insulating bushing surrounding the conductor comprising alternate layers of insulating and conducting materials and having one of its end portions shaped in substantially the form of a truncated cone, of a substantially discoidal shapcd conducting body extending laterally. from the conductor and disposcd adjacent to the smaller end of'said truncatcd-cone portion of the bushing.

12. .The combination with a conductor, and an insulating bushing surrounding the condnctor comprisng alternate layers of insulating and conducting materials, of a -condncting body extending transverscly of the condntor and so shaped as to insi1re a .substantially nniform distribution of e1etrostatic stresses upon the surfaces of the bushing.

13. The combination with a conductor, an insniating bnshing surronnding said conductnr and haring cmbcdded cylindrical condncting layers. and a conductinfg mcmber snrmundingsaid bnshing intorlnediat its Nuls. of a Ilut.toncd condncting body monnf ml upon said condnctor and having plane portions cxtending latcrally thcrefrom at one and of.thc lmshing and also having ts cdgcs ronnded.

In tcstmony whcreof, I have hereunto snbscribed my name this 31st day of July, 1911.

CHARLES LE G. FORTESCUE.

W itnesses:

R. (T. Dmnnonx, B. B. HINES. 

